This invention relates generally to chain tensioning apparatus, and more particularly concerns a mechanically ratcheting chain tensioner particularly well adapted to use on engines employing chains to drive cam shafts.
Currently-in-use chain tensioners on certain vehicles employ a hydraulic ratcheting design. Fluid on one side of a piston is allowed to flow through a small opening at the top side of the piston to the opposite side. As a result, when the piston tries to return, the fluid is not able to flow back through the opening because a small spring loaded ball seals the hole. One problem with such a device stems from the need for seals to prevent loss of fluid. Seal wear leads to malfunction and risk of expensive damage to the engine due to chain slippage or vibration. Further, such devices require very accurate fits and precision machining, leading to high cost. Avoidance of such problems has led to the use of adjustable bolts to tension chains, the bolts being locked after their adjustment; however, the problem here is the lack of automatic adjustment, so that a chain can stretch and malfunction before the need to adjust the bolt is detected.
Accordingly, there is a need for a device that is automatically adjustable, that has infinitely varying ratcheting capability, and that is not hydraulic, i.e. does not require seals.